Over the course of 2012 ENSO has moved from La Niña to El Niño state. Various ENSO forecasting models (see NOAA NECP, IRI ensemble below) now show Pacific equatorial SSTs anomalies will remain positive for the remainder of 2012 – albeit decreasing, possibly transgressing to negative temperature anomalies in early 2013 (NOAA NCEP) but within margins (±0.5C) of neutral ENSO state.

Whether or not it is correct to speak of continuation of a real El Niño may not be very relevant for the South East Asian regions possibly affected by SST anomalies [as the El Niño is mostly defined in the East Pacific].

Concerning the possibility of multiple dry months for peat forest regions on Sumatra and Borneo what is most noteworthy is a lingering El Niño state cold water SST anomaly around these two Indonesian isles (as can be seen below):

This is likely [and confirmed by NCEP precipitation model forecast below] to lead to below-average rainfall over the last months of 2012 – and, as the ITCZ descends to the southern hemisphere, possible progressive drought and above-average wildfire risk in the South East Asian tropical forest biomes.

When considering [for theoretical understanding] the size of the actual Indonesian cold water anomaly – which is small – it is important to view this relative to nearby warm SST anomalies, which lie both to the west (tropical Central Indian Ocean) and east (tropical Central Pacific Ocean) – meaning these regions may act as large-scale convection pumps, possibly draining depression activity away from the Indonesian region, which in turn is likely to experience above-average high air pressure, therefore below-average precipitation, hence (as from November onwards ITCZ (for Borneo especially) is already too far south): drought.

© Rolf Schuttenhelm | www.bitsofscience.org